I am really close to pulling the trigger on a Surface Book i5 with 128 GB storage (no DGPU). They are currently selling it for $749 refurbished.

My question is, if I go with the Surface Dock, can I run two 4K monitors at either 60 Hz or 30 Hz WITHOUT having to plug one into the surface itself. I'm cool with shutting off the monitor on the Surface Book itself to get the needed resolution.

The other possibility is to get the Surface Pro i5 with 4 GB ram and 128 GB storage which would perform better but have a much smaller screen and less battery life. I'd use my Surface Pro 4 keyboard and buy a new pen separately so I'd spend about $300 more.

I've also been looking at the iPad Pro 12.9 but I believe the Surface line is more functional for me and would let me sell my iMac, Surface Pro 3, and Mac Book Pro and basically just keep that device (which would ironically mean money in my pocket).

The cool thing is regardless of what I pick, I have an i3 Surface Pro 3 so the performance increase with either be double on the Surface Book or 2.5 times faster on the Surface Pro 2017 (and either one will be faster than my Mac Book Pro as well).